


Katekyo Hitman Reborn - Unthinkable

by Lowell



Category: Katekyou Hitman Reborn!
Genre: Alternate Universe - Age Changes, F/M, Romance
Language: English
Status: Completed
Published: 2019-07-26
Updated: 2019-07-26
Packaged: 2020-07-20 08:56:38
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,538
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19989469
Author URL: https://archiveofourown.org/users/Lowell/pseuds/Lowell
Summary: Reborn came into Tsuna's room to wake him up in the good old vongola style, as in the old days. However, he found a sleeping Tsuna with ... What is she doing here?





	Katekyo Hitman Reborn - Unthinkable

**Author's Note:**

> NOTICE:
> 
> The other character in the narrative is 16 years old (in my story).
> 
> Yes, it's a woman.
> 
> Who is it?
> 
> Read, just read!

Reborn smiled _sadly_.

He had just arrived from his last job at Tsuna's orders. In the mansion as always, maids keeping everything spotless, the chefs preparing breakfast, the guardians preparing for their daily duties, mobsters in suits performing the most varied tasks, Shoichi and Spanner in their lab as always, but had not yet seen _he_ still.

He didn't know where his student Dame-Tsuna was, who had a 10 am meeting with Baka-Dino. With all the habits he had gained from Reborn's spartan training, he woke up early naturally, or rather, as a survival measure his body and mind adapted, usually between 5 and 7 am depending on the day of the week. However, it was already 8:30 and still did not show the face.

Thinking of waking up like the _good old days_ , Vongola-style rose to his mansion room. It had been 4 years since Tsuna formally decided to accept Vongola Decimo's cloak, a mess and chaos was to make it happen, but one way or another it happened.

Now 18-year-old Tsuna living in Italy with his guardians and actively participating as a successor in Family business and slowly making the transition from ninth to tenth generation. And doing its best to make the mafia a better place, less bloodshed, a place where children can enjoy their childhood without inhuman experiences, despite all the obstacles, the result in such a short time is incredible.

Families naturally enchanted Tsuna for his principled and characterful actions, even though they were in a horrible world like the mafia did not let it shape him and always retaining their essence, various blood enemies became allies during the years Tsuna actively participated. from Vongola. Slowly, Vongola from the inside out, their allied families and progressively the whole mafia is undergoing a change. All thanks to a former civilian who holds the greatest power of all families. Especially the new generation, it is drawing inspiration from Vongola Tenth and its guardians with their rapidly increasing fame, becoming a leader and role model for everyone.

Reborn is proud of his student, although he doesn't say it out loud often. One look is all he needed to convey this and every once in a while it didn't hurt a compliment. Lie, it does hurt.

Finally coming to his room and kicking the door to wake his pathetic student and torture a little. Pouring water in the face, maybe firing a shower of bullets, waking up using the defibrillators, using your good old Leon hammer on him. The possibilities were various.

However, to Reborn's surprise the scenario ahead made him perplexed. He did not expect the reality before him, his mind wanted to uncover it and not process this information.

In the bedroom, on a huge king-size bed is Tsuna wrapped in a white blanket with her sleeping upper body naked and with a somewhat relaxed expression. But what caused the chaos in Reborn's brain was that Tsuna is hugging someone in bed. And that person is…Yuni!

YUNI!

THE EX-ARCOBALENO SKY!

THE BOSS OF THE ARCOBALENO!

FUCKING WORLD!

How did this happen? How is Tsuna sleeping with Yuni? How did nobody notice? Reborn didn't notice or know anything that pointed this out, a kiss on the lips or longer on the cheek, blushing each other, love letters, messages, gifts, missing at night and if Gamma somehow suspected this case, obviously he would know. But somehow supernaturally, Tsuna is sleeping with her arms around Yuni who had a… affectionate smile on her face… what the fuck is that?

And how was Yuni at Vongola mansion? He knows no one came to visit anyone yesterday and Tsuna has just arrived from a 7 day trip.

Reborn's doubts and uncertainties only accumulate more by the second as he tries to come up with a logical and reasonable explanation for this. Resolving to question the two, he picks up two cushions from the couch and throws them in the face with murderous intent (certain habits never die).

Tsuna opened her eyes and as fast as lightning grabbing the two pillows, while her orange eyes showed caution looking for any threat ahead. Until it stopped at a 6-year-old in a black suit and a fedora popping an orange ribbon around it, holding a green chameleon in his right hand. His expression didn't betray his thoughts, with all the hell he spent with Reborn he knew how to control himself.

'HHHHHHHHHIIIEEEEEEE 'Chaos unraveled in his mind wondering how it happened, how Reborn came in, why he came in first, and what he would have to explain about this peculiar situation.

After all what was the Tenth Vongola of the Mafia's largest family and the current boss of Giglio Nero, the former sky arcobaleno, were having an affair. This news within seconds of escaping this room would shape rumors and everyone would know in less than an hour and no doubt the chaos would come.

Reborn didn't want to imagine it now, it would probably take some time for everything to settle in and between the two families.

An innocent Yuni opened her eye "~ Tsuna?" Tsuna was standing in bed with only a pair of shorts on, thank god he had something. His eyes glowed orange, just as baptized by Yamamoto Takeshi, _the mode boss's_ , meaning some serious situation.

Sitting lazily and looking at the lover who was… pale and white? She followed his line of sight until he found the reason. Yuni was stunned and unsure how to react, sat up hurriedly, grabbed her blanket and pulled against her chest trying to get a word.

"O-Oji-sama," he whispered, but Reborn listened. "Yuni, Dame-Tsuna, you better explain what's going on!"

Yuni and Tsuna exchanged terrified looks wondering exactly how to count until they were interrupted by a click of a gun. The biggest killer in the world is very angry with his niece and his student "Speak _now!_ "

"Yuni and I are dating" The Tenth Vongola miserably responds to her tutor's terror, after all her Reborn traumas haven't left yet, even worse the angry killer.

Reborn's mind shut down and back trying to connect the dots as and where it happened. But you have an even more important question to ask, "How long?" He growled at both of them.

Yuni whispered with her body behind the cover, just dressed in a white Tsuna dress shirt covering her... "6… 6 months" She's probably… Reborn didn't want to think about that, not right now.

"Are you dating a half year?" Was much more of a thought than a question. Like in 6 months he didn't realize it, there should be some sign of it somewhere, a kiss, a hug, a letter, a long meeting, some of them fading, Tsuna having some reaction, Yuni blushing at some point with him, but nothing! How did they do it? In reality how were they here without anyone noticing? How did Gama not notice that her princess had disappeared from her mansion and how none of the other guardians seem not to know it?

Reborn was secretly proud of his student for this achievement. Not that he would admit it.

"Explain, how it started, how you are here and how no one noticed your relationship." Reborn kept the gun aimed at Tsuna, he was not going to point at his niece.

"It started at 6 months in the annual family party" Reborn remembered this party, Tsuna led her as head of the family, everyone was there, his guardians, arcobalenos (yes, everyone, even Verde decided to go, somehow he would have fun for his experiments and could enjoy a good conversation with Shoichi and Spanner), Cedef, Dino and his family, Byakuran and his guardians, was not just limited to his family, but whom Tsuna recognized as a friend and somehow the marshmallow. entered this classification.

Even Varia who does not obey anyone appeared and began to respect Tsuna after he officially accepted his post.

That was an interesting story that no one knows the answer to. From one moment to the next, the relationship of Tsuna and Xanxus who were enemies to allies in the same family evolved into legitimate uncle and nephew. Everyone was surprised when Tsuna suddenly called Xanxus _Zio(uncle)_ and the other just accepted, not throwing drinks or throwing bullets at him, but kept the _Trash_.

Curious Reborn once asked Tsuna, the answer was somewhat intriguing _"No big deal"_ But his expression held that when something big happened, something big and complex that somehow Tsuna and Xanxus were together in this situation that strengthened their ties.

And finally, Giglio Nero, Reborn recalls that Yuni went along with Gamma and other guardians. But he does not remember at some point that Tsuna disappeared and Yuni at the same time… Until reflection came to mind and connected the dots.

Obviously, this set of people could not stay calm and without breaking anything for long, incredibly lasted 4 hours without something happening. But when a minor incident occurred, it was Gokudera Hayato arguing with Squalo for something frivolous and chaos broke out. Reborn happily stepped into that mess of drinks, flames and bullets flying back and forth. At that moment, he knew who wasn't fighting and among them, there were Tsuna and Yuni. Probably at that time.

Reborn mentally felt disappointed in himself, he always knew when something big happened to Tsuna, his boss, his sky.

Was Reborn even more curious how they managed to hide their relationship and how Yuni was in this mansion without anyone knowing? How did Gamma not know that?

"How are you here? Does Gamma know this? Does anyone know that?" Reborn asked looking deep into their eyes. "Nobody. You're the first. "Tsuna sat on the bed.

"About how Yuni is here is simple, I picked her up yesterday" Tsuna casually said.

Reborn narrowed his eyes and realized his student continued "We were two weeks without seeing each other and when I came back and realized that we were both in the same city I went to get her" Yuni moved to Tsuna's side dragging the blanket along, blushing slightly.

Yuni was 16, over time the childish curves she had lost, her body slowly gained refined and temperate curves with training (yes, it was Reborn), her long hair reaches half of her back, her bust grew considerably. Making her attractive to several suitors who sent her marriage proposals and her buttocks gained new proportions making her a beautiful and sensual woman.

She turned into a beautiful woman just like Luce, her grandmother, and Aria, her mother.

Wait, Tsuna escaped without anyone noticing?

"Did you leave the mansion and fly to her and come back without anyone noticing?" There was a tone of excitement and disbelief simultaneously. Tsuna nodded her head.

Reborn had to score points for his student, that was an incredible feat, and even though he didn't want to admit it, the world's greatest killer didn't realize his unofficial travels to the Arcobaleno princess. No doubt this was not the first time, meaning no one in all of Vongola noticed their boss disappearing. Now there were certain guardians and guards to train in hell for not noticing him disappearing.

But the most important question "How did you hide your relationship so far?" Tsuna and Yuni exchanged a look and smiled "We didn't hide" The both say.

 _Hã?_ It makes no sense. If not, there should be some sign at some point of living together. Unless no one considered the possibility of a romantic relationship between them and simply ignored when they were alone.

Wait, was there anyone who might know "Byakuran do you know?" The three regularly hang out together, if marshmallow were the couple's cover for dates it would make sense.

"We honestly don't know, sometimes when we leave, he disappears out of nowhere and we would hardly find it. So it turns out to be a date, but we always bump into him at some candy store buying marshmallow. "

A mystery solved "You are not hiding your relationship. Just no one notices that when you go out on a date together, right?" They both nodded.

Another mystery solved, bunch of fools who don't notice that. Reborn thinking about their reactions when they find out about this couple. Better yet, they never noticed all the signs in front of them. Their expressions will be epic, especially the arcobaleno' disbelief and Gamma's pain at losing their _untouched_ princess.

Right, however, there was a question to be asked, "You used condoms, right?" Reborn didn't want a possible war between the two families over an heir, not now. The tone was terrifying and obviously not a question. They both blushed fifty shades of pink before nodding their heads.

"How did Gamma not suspect you were gone, Yuni?" This was something Reborn was dying to find out, Gamma with all that father-protectionism about Yuni wouldn't easily let his missing boss pass, probably by now he would have launched a search for the 6 hells behind her.

"Gamma won't come into my room unless I call him or it's an emergency and yesterday I said I'd like to sleep in the morning. Until Tsuna kidnapped me. He probably didn't realize it yet. And when we woke up Tsuna would take me back."

Reborn added another person who deserves to get hellish training for not repairing his missing boss and saluted Tsuna for the stealth.

The relationship is reciprocal and stable for a few months, both are comfortable and Reborn doesn't see why intervening in it. "Promise me, you won't pit me against each other." of couples were unpredictable and sometimes had corrosive side effects on others.

"We promise," they both said. "Aren't you going to… torture, shoot or threaten me?" Tsuna said apprehensively.

Reborn sighed, as much as he would like to do that. "No, you make your own choices." He lowered the gun to Leon.

Tsuna and Yuni sighed, relaxed their shoulders, letting the tension go. Facing the world's biggest killer angry is something no one would like. "Now, Dame-Tsuna, go get ready, you have a meeting at 10"

Tsuna looked at Reborn until he noticed, "There… Reborn, Dino-nii called me last night asking if the meeting could be at 2 pm. How you arrived early today has not yet been informed. "

That means… Reborn only found out that couple was dating by accident and it was thanks to Baka-Dino. He made a mental note to increase his vigilance in everything. If he let it go, maybe there is some other situation.

Reborn's mind began to think of the possibilities this relationship might make until a smile descended on his face "Alright, Tsuna come down for coffee until 10 and Yuni, I'll call Gamma telling you I kidnapped you" Tsuna's expression went pale as he knew exactly what Reborn is doing.

"You're going to cover us up so no one can find out and you can have fun later" Reborn smiled innocently "What are you talking about?"

Tsuna sighed in defeat, he knew there was no way to stop a mess when someone found out about his relationship with Yuni. But of all possible people, it was Reborn. He knew the excitement will now be exponentially greater. All he could do is prepare for chaos.

Reborn walked toward the door "Good morning, _lovebirds_ " Making fun of the couple who blushed at the statement. He would make the most of their new relationship.

The door closed and the pressure finally ceased. Tsuna fell down on the bed and Yuni collapsed in his chest "I thought he was going to put bullets in my body"

Yuni laughed adorably at her boyfriend who almost had a fit when Reborn came in "Fortunately, Oji-sama gladly accepted, but..." Tsuna moaned "I know" He say.

It was a matter of time before Reborn came up with a scheme to tell everyone in the most flashy and potentially dangerous way. They weren't necessarily hiding from anyone, just nobody noticed the new relationship… Friends and family questioning them were in their future soon.

Wanting to put it aside Yuni got up and sat on top of Tsuna giving a sharp and seductive look, unbuttoning his white social shirt throwing in some random corner "So… we have a free hour and a half…" his hands running over her long straight dark hair from top to bottom and finally falling on boyfriend's chest.

With the sight above him, his naked girlfriend _on top of him_ , running his own hands over his body softening his sensual curves and teasing him further. A seductive look that says she wants him and undeniably Tsuna wants her, _especially in this situation._

"My only priority now… is you." Tsuna sat holding her on his lap wrapping her arms around his waist and pulling her close, bringing their faces closer to feel her breath, the unique warmth her skin provides. Then instincts and the irrationality of desires took over her córtex.

Immediately kissing her, wet, wanting to fight for the space in each other's mouths, their tongues rudely trying to gain territory and mutually bringing a thousand stimulating sensations. Instinctively, Yuni wrapped her hands around his neck, pulling harder. Tsuna squeezed her, her naked body touching each other, her chest bumping and rubbing against his as they endlessly sought pleasure was a pleasant and exciting sensation.

Eventually their mouths split to take air leaving a saliva line. Wasting no time, Tsuna began to suckle relentlessly on her neck, loving to see how Yuni moaned with each advance, stronger and more provocative, especially when she said his name, the pleasure only increased and that only served to excite him more.

Finally, catching his breath with his lips millimeters from each other, writhing so as not to shock and invade his mouth with his tongue searching for his partner for endless pleasure. "For a morning that could have been hell… until it's being a _beautiful_ morning "Tsuna teasing her.

Yuni approached her ear and said in the most seductive voice possible "So make this morning even more _beautiful_ " Tsuna smiled mischievously, answered and fulfilled his desire… with actions, her face expressions, her moans, the possessiveness they had. They had each other at such moments, their bodies constantly in close contact, their voice soft and sensual when he called his name.

All this, is a part that Tsuna loves in her.

In that small space of an hour and a half, they had their moment, every second was effectively used to produce pleasure for each other, to satisfy the urge to take their lover to themselves, their desire to be just one, an ardent confrontation of each other. two naked bodies clashing unable to suppress their will or move away, an intense and hot morning happened. The weeks they spent separated by appointments, meetings, and urgent matters were all being brought up to date.

Tsuna is hers and Yuni is his. This became an unchanging truth 6 months ago, but this is something no one knew yet except Reborn.

9:40 in the morning.

Tsuna after much ardent and intimate action with Yuni, decided to shower together. Sitting in the tub and enjoying the water at the ideal temperature, Yuni on his lap resting his head on his chest and Tsuna with his hands skirting her waist.

"What do you think Uncle is going to do?" Yuni with his eyes closed while enjoying the bath, told his boyfriend.

"The basic idea is that he should have fun with my suffering and everyone's reactions. Any scenario that maximizes this is an option." Several possibilities went through his mind.

"He can hide our relationship until he acquires compelling evidence and then use it to create the ideal situation he wants."

"What would it be?" Yuni curious "You better not think. Just get ready for the inevitable." Tsuna took a deep breath knowing something would happen soon.

"Right. There is another inevitable thing that will happen now. "She turned to Tsuna and lay on top of her body. The two in the tub, both naked bodies, her chest rubbing against his, incredibly soft and a wonderful sensation took over her mind.

"We still have 20 minutes. Is the joy over, Vongola Tenth? "Yuni's seductive voice rang in her ear causing goosebumps.

All that was left in that bathroom, on the walls, were the sounds of Yuni's constant moans and a fiery Tsuna unable to control her sexual desire.

"..."

Elsewhere in the mansion, Reborn is in his chair sipping the highest quality coffee he could find on the market, had just told Gamma that he had kidnapped Yuni and obviously the lightning keeper was not happy about it.

Thinking about the number of possibilities that maximizes his enjoyment while torturing his student and enjoying everyone's reactions. Being curious as to how Tsuna would get around Gamma who is basically Yuni's father.

However, there was a thought that made him even happier when he realized _he has_ a wedding to plan for his student and his lovely niece. With a smile on his face he got up and walked out of the room.

_There were preparations and soon a wedding to plan… Vongola-style, totally out of the ordinary._

**Author's Note:**

> Imagine this situation in manga or anime. I wondered and thought how funny it would be.
> 
> Yuni in the original story is 10 years old, in this case she should be 14 years old, but to have a relationship with Tsuna 18 years old ... would be very unequal, so in my story she is 16 years old, just two years apart.
> 
> If out of curiosity, one cannot imagine a Yuni with a curvaceous body. Remember mom and your grandma, she's 10 years old with that kid designer. When it obviously grew your body would develop ... Imagine.
> 
> Now the chaos this will cause is something that is in my head and it would be fun to write about.
> 
> Mainly among the guardians of Tsuna, the arcobalenos and Gamma.
> 
> Only after writing the story did I notice that I left Yuni full of attitude and honestly, these are usually the best.
> 
> Leave your comments of possible chaos or any other Vongola-style situation!


End file.
